Organic materials, whether natural or synthetic, are conventionally protected against degradation by ultraviolet (UV) light by incorporating a UV light stabilizer in the material. Many classes of compounds are known to be useful UV light stabilizers, some being more effective than others. Particularly effective compounds which provide compositions resistant to degradation by UV light, include the decahydroquinolines disclosed in U.S. Pat. Nos. 3,919,234; 3,920,659; 3,928,330; 4,069,195; and, 4,073,770; 1,5-diazacycloalkanes and 2-keto-1,5-diazacycloalkanes disclosed in copending U.S. Pat. application Ser. No. 835,069; and, the 2-keto-1,4-diazacycloalkanes disclosed in copending U.S. Pat. application Ser. No. 835,065. Other cycloalkanes useful as UV light stabilizers are disclosed in German Offen. No. 2,315,042; and, Japanese Pat. Nos. 7,453,571 and 7,453,572.
The foregoing compounds appear to derive their effectiveness as UV stabilizers from their mono-keto structure, that is a 2-keto-1,4-diazacycloalkane structure, in which a total of two or more (hence "polysubstituted") substituents are provided on the carbon atoms on either side of, and immediately adjacent the N.sup.4 atom of the diaza ring (hereafter referred to as "the N.sup.4 -adjacent C atoms"). Even on a laboratory scale, polysubstituted 2-piperazinones with substituents on the N.sup.4 -adjacent C atoms are difficult to prepare, particularly if they are to be formed to the substantial exclusion of compounds which do not contain substituents on the N.sup.4 -adjacent C atoms. For example, the polysubstituted 1,4-diaza-2-keto-cycloalkanes disclosed in the aforementioned references, and also the dispiro substituted diazacyclohexanes arduously synthesized in U.S. Pat. No. 4,097,452 to Mayer et al., can be conveniently and economically prepared, with the ratio of substituted compounds having substituents on the N.sup.4 -adjacent C atoms to those without substituents on these C atoms, being in excess of 20:1 by weight. In copending U.S. Pat. application Ser. No. 916,640 now issued as U.S. Pat. No. 4,167,512 several methods are disclosed for preparing various substituted piperazin-2-ones and 1,4-diaza-2-keto-cycloheptanes, all of which methods are incorporated by reference thereto as if fully set forth herein.
The effectiveness of the instant reaction, referred to as "the cyanohydrin acetate synthesis," is particularly noteworthy because it is known that a hydroxyl group will react with dichlorocarbene, but it is quite unexpected that an acetate group would react in the same way. Hydroxyl and acetate groups are known not to behave similarly in most reactions. Further, because of the presence of alkali metal hydroxide, acetone cyanohydrin forms an anion which appears to be essential for the completion of the cyclization of the diaza ring. However, acetone cyanohydrin acetate does not form such an anion, whether in the presence of alkali or not, so that the cyanohydrin acetate would not be expected to react in a manner analogous with cyanohydrin.
Particular reference is made to a known synthesis referred to as "the cyanohydrin synthesis," wherein a substituted 1,2-diamine is reacted in an organic solvent medium with cyclic or acyclic cyanohydrins in the presence of an "onium salt" (defined hereinafter) catalyst, to yield a polysubstituted 2-keto-1,4-diazacycloalkane. The cyanohydrin acetate synthesis of this invention is an improvement of the aforementioned cyanohydrin synthesis.